<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>弹性盒布局</title>
    <style>
        body {
            background: rgba(255, 0, 0, 0.2);
        }

        header, footer {
            height: 100px;
            margin: 0;
            padding: 0;
            border: 3px solid rgba(239, 150, 5, 0.8);
            border-radius: 6pt;
            line-height: 100px;
            text-align: center;
            font-size: 30px;
            font-family: 楷体;
            color: rgba(239, 21, 13, 0.8);
        }

        main {
            margin: 10px 0 10px 0;
            padding: 0;
            /*border: 3px solid red;*/
            /*border-radius: 6pt;*/
            height: 400px;
            display: flex;
        }

        aside, nav, article {
            font-size: 30px;
            font-family: 楷体;
            color: red;
            border: 3px solid darkred;
            border-radius: 6pt;
            text-align: center;
            line-height: 400px;
        }

        aside {
            order: 1;
            flex: 1;
        }

        nav {
            margin: 0 5pt 0 5pt;
            order: 2;
            flex: 2;
        }

        article {
            order: 3;
            flex: 1;
        }
    </style>
</head>
<body>
<header>页头</header>
<main>
    <aside>左侧栏</aside>
    <nav>导航栏</nav>
    <article>右侧啦</article>
</main>
<footer>页尾</footer>
</body>
</html>